Saturday, March 26, 2011

The Meteor of 1860

The folks in eastern North Carolina got a good show Tuesday evening (3/22/11). Apparently, a huge meteor went streaking across the sky. Residents of Pender, Brunswick and New Hanover Counties reported the huge fireball with a glowing fiery tail at about 7:30 PM.

In the 19th century, the Honorable Thomas L. Clingman became one of the most unique figures ever in the scientific exploration of the southern mountains. Over his career, he did a lot more than just measure the tallest summits. Nothing would stop Clingman in the pursuit of answers. He must have traveled thousands of miles across the mountains to investigate one mystery or another, whether it was on Peek’s Creek in Macon County or Fine’s Creek in Haywood County.

His article, THE GREAT METEOR OF 1860, appeared in the January 7, 1871 issue of Appleton’s Journal. I’m not reposting the entire article, but these excerpts display Clingman’s methodical approach to the subject:

On the 2d of August, 1860, I was at Asheville, Buncombe County, in the picturesque mountain-region of North Carolina. On the evening of that day I retired to my room a little after ten o'clock. The moon was full and approaching the meridian, and the night was clear and bright. There was a window on the west side of the room covered by a white curtain.

The candle having been extinguished, my attention was suddenly arrested by a bright glare of light. It was much brighter than a candle would have made, and seemed like a sheet of flame against the window. With surprise and alarm I went toward the window, but before I reached it the light suddenly changed its color and became beautifully white. The thought at once flashed upon me that it must be a meteor, and I saw its out line through the curtain as it exploded in the northwest. The light at the moment of explosion seemed as white as that produced by the burning of the metal magnesium. During the whole period that I observed the light it was greater than hundreds of moons would have caused.

On the next day, I made inquiries of many persons who had seen the meteor. It was observed by a large number, because the evening was that of the election-day, and also because there was a party of gentlemen then on horseback in the town to receive General Lane, whose coming was expected. They all concurred in saying that the meteor was first seen in the southeast, but at a point nearer to the south than the east, that it moved toward the northwest, and when due west of Asheville appeared to be at an elevation of forty or forty five degrees, and that it seemed to explode in the northwest, with a great display of light. Most persons regarded it as appearing to be equal in size to the full moon, and all agreed in saying that the moon light was nothing in comparison with its brightness. When first seen in the southeast it seemed of a dull or pale red color, and became brighter as it moved along until it resembled the sunlight. Persons from the surrounding country made similar statements as to its appearance.

Colonel C. M. Avery, who saw it while in Morganton, sixty miles to the east of Asheville, described it as not materially different in position and aspect; while persons in Franklin, seventy miles west of Asheville, spoke of it in similar terms, except that it seemed to them higher in the heavens to the west, and more nearly over them. In a few days the newspapers from Knoxville, Tennessee, and from Columbia, South Carolina, came to hand, with similar descriptions, representing the meteor as having passed on the west side of both of those places.

Clingman went on to enumerate sightings of the meteor, reported (telegraphically) from such far-flung locations as Raleigh, Pittsburgh, Nashville, Memphis, and New Orleans. He even returned to a location in Raleigh with one eyewitness in order to identify the exact path of the meteor:

A few days after I read Mr. Moore's precise and elaborate statement, he and I went to the spot where he had stood at the time he saw the meteor. By means of certain trees and houses, he was able to indicate the line along which it had travelled. By taking the directions with the aid of a compass, it was shown that he observed the meteor when it was twenty-four degrees south of west, and that the point where it was last seen by him was also when it was twenty-four degrees north of west. He saw it continuously as it passed over these forty-eight degrees, but, Holly Springs being a little south of west only, he necessarily saw it at the time when it was in the direction of that place, and he estimated its height as being thirty degrees above the horizon.

Clingman proceeded to correlate this information with similar reports from other locations to estimate the distance at which the meteor entered the earth’s atmosphere:

When all the statements published are considered, there would seem to be no reason to doubt but that this meteor, when distinctly seen between Raleigh and Holly Springs, was more than one hundred and less than two hundred miles above the earth's surface. If, therefore, the common opinion be true, that meteors are rendered visible only by passing through the earth's atmosphere, then that atmosphere must extend much more than one hundred miles from the earth's surface.

This very meteor affords a strong proof of the correctness of this conclusion. It exhibited at first a pale or dull red color, became gradually brighter, till it attained a silvery whiteness, and then exploded with brilliant coruscations, and, as it moved on, repeated these explosions several times. This would be accounted for on the supposition that a body originally cold was, on entering the atmosphere, heated by the friction caused by its rapid motion, at first becoming faintly luminous, and then growing brighter until its surface became so intensly heated as to generate gases, and thus cause explosions, throwing off fragments from its surface, and, as its successive coats be came heated in like manner, repeating its explosions till it passed out of the earth's atmosphere, or was finally shivered to pieces.

When this meteor was first visible, it must have already passed for some distance through the earth's rarefied atmosphere, and have dipped deeply into it. It would therefore seem to be almost certain that the atmosphere must extend more than one hundred miles from the earth's surface, and probably much farther.

Using a similar investigative approach, Clingman also considered the size of the meteor and the transmission of sound from the object hurtling through the atmosphere. Here’s the remainder of his article about the meteor of 1860:

I will now advert briefly to the statements as to the size of the meteor. On this point the evidence is not so conclusive. Persons are liable to be deceived by the appearances of bright lights with respect to their real size. Mr. Moore says, when first seen, it appeared to be only six inches in diameter, but; when at the nearest point to him, he estimated it to appear thirty feet in diameter, and of some hundreds of yards in length. He lays much stress on the solid appearance of its light, it being well defined and without any irregular edges. Others say it looked like a railroad train, while some say it was as large as a barrel. Mr. Ingraham and others at Holly Springs say it was in size fully equal to the disk of the moon when full. A similar estimate was made by observers at Antioch College, Ohio, and at Pittsburg, Pennsylvania.

If a body at the distance of three hundred miles should appear as large as the moon, it ought to be nearly three miles in diameter. As this meteor was throwing off luminous gases, it would of course appear larger than it really was, especially after it became intensely heated; but, when its color was dimmer than that of the moon, the deception ought not to be so considerable. It is also true that the observers generally say its bright ness was greatest after it had passed and had receded from them. The amount of light it gave also indicates its great size.

Major Francis Logan, of Habersham, Georgia, and R. N. McEwen, then at Athens, Tennessee, nearly under its line of movement, represent it as being larger than the moon, white, "like melted silver," and throwing a light upon the earth "like that of the sun." And yet its bright ness is described in terms almost as strong by persons at Holly Springs, more than three hundred miles distant. At Nashville and other points they speak of this light as sufficient to enable one to pick up a pin. Could any but a large body cast such a light over so great an extent of country?

But the most perplexing part of the subject is the rapid transmission of sound from this meteor. Colonel William M. McDowell (who was then and for several years previous making observations, for the Smithsonian Institution, at Asheville) stated to me the next morning, that, being on horseback and looking downward to the earth, which was already bright in the light of the full moon, he heard a rushing or hissing sound, and, on looking up, he observed the meteor in the southeast, presenting at first a dull-red color, and rapidly becoming brighter. Several other gentlemen in Asheville also declared that they heard such a sound distinctly, and at first supposed the meteor to be a rocket sent up. There were, however, in fact, no rockets at Asheville, nor was there any expectation that they were to be discharged.

Dr. J. F. E. Wordy (who has since the war been making the observations for the use of the Smithsonian Institution) was then in the piazza of Mr. Cheesboro's house, two miles southeast of Asheville, and declares that he not only saw but heard the meteor while it was in sight. Being somewhat deaf, he asked the members of the family if they heard it, and had an affirmative reply from all present. Colonel John A. Fagg, who had on that day been elected a member of the Legislature for Madison County, and who was then in the town of Marshall, twenty-one miles distant in a northwestwardly course, declared to me that he heard the hissing sound plainly while it was passing.

Mr. J. H. Ingraham, writing from Holly Springs, says its passage was accompanied by a hissing sound, if the testimony of a great number of persons was to be relied on. Mr. W. C. Knapp, of the same place, says it was accompanied by a hissing noise. Mr. H. A. Preston, who writes from Antioch College, Yellow Springs, Ohio, says a faint hissing sound was distinctly heard. Major Francis Logan, of Habersham, Georgia, says that persons there generally spoke of hearing it during its passage in the same manner. Mr. R. N. McEwen, who was then at Athens, Tennessee, says that he and his wife, being in the piazza of his house, were both confident that they heard a hissing sound as it passed over them.

Seeing its brilliant explosion after it had passed toward the northwest, thinking it only two or three miles distant, they remained standing for some time in expectation of hearing a report, but not until after they had gone into the house, and, as he supposed, an interval of fifteen minutes had elapsed, was there heard a prolonged sound, as the report of a large cannon. A gentleman, who lived near Asheville, stated to me the day after the meteor had appeared, that, on seeing the explosion, he paused in the road for a little while, in expectation of hearing a report, but that he walked afterward nearly around his farm, and, after an interval, he thought of at least fifteen minutes, had elapsed, a heavy sound came from the direction of the meteor.

We have thus the statement of a number of intelligent and trustworthy persons who were separated hundreds of miles from each other, all affirming the same fact. But as sound is ordinarily estimated to travel but little more than eleven hundred feet in a second, the meteor might be supposed to have been out of sight of those nearest to it, for at least eight or ten minutes, before the sound created by its passage could have been heard. Were they all mistaken in supposing that they heard it while it was in sight? Is the ear much more likely to be deceived than the eye? Are not persons generally as confident that they hear the thunder as that they see the lightning? Why should all these persons imagine that they heard such a sound when it is not usual for meteors when so seen to be also heard?

Two of them did expect to hear the explosion, and waited for it without imagining that they heard it at the time when they expected it, and only heard it long after they had ceased to look for it. It is but natural that we should hesitate to believe as true what is at variance with general experience and with what seems established in science. Solid bodies had often been seen to come down from the higher regions of the atmosphere, before scientific men accepted the fall of meteorites as an established fact. But the circumstances under which these sounds were manifested were peculiar, and are not neces sarily to be assumed as contradicting our general experience. In this instance a large body was moving with very great rapidity through the atmosphere.

We can only approximate in our estimate the speed with which this meteor moved. While some observers regarded it as being from six to ten seconds in sight, the longest estimate of its visibility is that of Mr. Ingraham, viz., twelve to fifteen seconds. He and others with him at Holly Springs saw it in the southeast, and until it had passed to the northwest. One writer says it disappeared west of north. It must therefore have been seen to move through a space to be measured by more than a hundred degrees, and it might have been much more. As the meteor, considering its elevation above a place on the earth's surface at least three hundred miles off, was at the nearest point farther from the observers than that distance, if it moved through one hundred degrees of space in a right line nearly, it must have been in view while it was passing through a distance of six or eight hundred miles. Such a calculation would make its speed from forty to sixty miles per second, depending of course upon the accuracy of the estimate of the time.

It could not have been describing a curve around Holly Springs, because it was at the same time seen by the observers in Ohio, Pittsburg, Pcnnsylvania, and Caroline County, Virginia, in its course to the northwest. Mr. Moore, who was at Raleigh, on the opposite side of the meteor's track, and probably about the same distance from it, saw it pass through forty-eight degrees by measurement in eight seconds, as he estimated the time it was in view. Its speed, calculated from these data, would approximate fifty miles in a second. As it appeared to be moving in the part of its course seen by me, it seemed certainly not less rapid. Might not a body moving with this velocity generate a rapid transmission of sound?

If we assume that there is some highly-elastic medium through which light and electricity, for example, are propagated, might not this body, by the suddenness of the impulse it gave, propagate a sound to a great distance with such speed? But it may be said that lightning moves with very great velocity, and that yet the noise of the thunder travels with only the speed of other sounds. It is true that, when the flash is near, the thunder seems louder to the ear than any other sound, and yet it is propagated to the distance of only twelve or fifteen miles. On the other, hand, though, when one is near a large cannon, its report does not seem so loud as thunder, yet it can be heard to a much greater distance.

When, during the late war, I was at Charleston or Savannah, I could in favorable states of the atmosphere distinctly hear the guns at the other place, though the two cities are understood to be one hundred miles apart. The cannonades at Charleston were often heard. in the upper portions of South Carolina, while those at Richmond, Virginia, were sometimes heard west of Greensboro, in North Carolina-in each case at a distance of nearly a hundred and fifty miles. Why is it, then, that, though thunder seems louder than the reports of artillery, it cannot be heard so far?

The explanation does not seem to be difficult. If a pistol be discharged into the water, the bullet breaks the surface violently, and causes the water to be sprinkled for a short distance; but the ripple produced on the surface extends but a few feet around. When, however, the steam-frigate Minnesota was launched at the Washington Navy-Yard, though she glided so gently into the water that she did, not break the surface apparently, yet she caused a wave which extended itself across the harbor, and rose several feet on the shore opposite, wetting many persons who were there to see the launch.

As an illustration on a still larger scale, I refer to the fact that earth quakes in Japan cause waves which are propagated across the Pacific Ocean to the shores of California. A large body, though moving slowly, creates a wave which extends to a great distance, while a violent impulse of a small one produces no such result.

From the smallness of the furrow produced by lightning through the bodies of trees struck by it, and from its passing so readily along a small rod, it would seem that the volume of air displaced by it is small, and analogous to the effect caused by a pistol-shot on the water; while the explosion of gunpowder, when a large cannon is dis\ charged, produces a greater displacement of the atmosphere, causing a large wave of sound, which is extended to a great distance, as the wave in the water caused by the Minnesota was perceptible for miles. But, when the ship was launched, though a larger portion of her bulk was in the air than in the water, yet she did not make a corresponding wave in the air which could be felt across the harbor. Even a railroad-train, moving much faster than did the Minnesota, does not send in advance of it a great wave in the air. But, in fact, air is capable of receiving such an impulse.

When a large gun is discharged, such motion is given to the air that houses are shaken and window glass broken. As air, therefore, is much rarer and more elastic than water, it seems that it requires a much more sudden impulse to create an extended wave in it than in water. If, then, it may be regarded as a general law that the greater the rarity and elasticity of a medium the more sudden and violent must be a force sufficient to produce a movement that will be extensive, then it might well be that the expansion of gases generated by the explosion of gunpowder would be too slow to affect a medium as much rarer than common air as that air is rarer than water. But a much more sudden and violent movement might possibly cause an impulse in such a medium that could be perceptible at a great distance.

A cannon-ball, propelled with the ordinary charge, is barely driven a mile in five seconds. If we take forty miles per second as the velocity of this meteor, it moved with a speed two hundred times greater than that of a cannon-shot. A spherical cast-iron shot weighs about two hundred and twenty-five pounds. If the meteor be assumed to have had a diameter of one mile, its surface, and the consequent volume of atmosphere displaced, would have been more than twenty-five million times greater than that of the cannon-ball. And, as its solid contents were in bulk more than five thousand times greater than this number indicates, the resistance of the atmosphere would be trifling in comparison with that to the cannon-shot.

Even if the diameter of the meteor were but one hundred feet, its surface would have been ten thousand times greater, and its bulk one million times larger. Such a body, moving with a speed two hundred times faster, would present a condition of facts with which we are not at all familiar on the surface of the earth. The hissing sound described reminds one somewhat of sounds occasionally heard when electricity is passing along imperfect or non conducting substances. If electricity be coextensive with the atmosphere, this meteor might have produced great accumulations and disturbances in it, and caused vibrations to great distances.

That these should be very rapid would seem to be probable from the fact that the greater the rarity of the several gases the higher the speed with which sound is propagated through them. Mr. McEwen, at Athens, heard the hissing sound while the meteor was in sight; but fifteen minutes elapsed before the report from the explosion reached him. The explosion was doubtless caused by the intense heat at the surface of the meteor, which generated gases, the expansion of which threw off the outer coating of the body in fragments.

These gases ought to be expected to expand with a force and speed equal to those caused by the explosion of gunpowder. This has not, I think, been estimated as quite equalling one mile per second. Such a movement would, therefore, be slow, compared with the velocity of the meteor itself. Hence, while the hissing sound caused by the latter might move with the rapidity of electricity, that caused by the explosion would travel only with the speed of such sounds as we are familiar with, and would therefore reach a person one hundred and eighty miles distant in fifteen minutes.

***

Just as an afterword to Clingman’s theory of two types of sound generated by the meteor, I can add the following. Apparently, current science confirms that Clingman was about right. A meteor entering the atmosphere ionizes the air around it. With soaring temperatures from friction with the atmosphere, a glowing plasma trail forms behind the meteor. As the plasma cools, ions and electrons set off VLF vibrations that transmit electromagnetic waves over great distances. Under the right circumstances, the sounds might be audible to humans. Indeed, many eyewitnesses to meteors report a hissing or sizzling sound simultaneous with the flash across the sky. *

For the second type of sound, it is correct that a large meteor can generate a sonic boom that would lag behind the actual fireball by seconds or even minutes.

And then there are the Voyager Sound Recordings: complex interactions of the cosmic plasma of the universe, charged electromagnetic particles from the solar wind, planetary magnetosphere, rings and moons create vibrations detected by the Voyager, the vibrations are converted to sounds heard on a recording later released as "Symphonies of the Planets, The Voyager Recordings":